"Had such a policy been in place when some of the signatories to this letter were considering coming to this country, they might have chosen not to come at all, or would not have been allowed to remain."

The policy, which is still being formulated by an independent committee, would see any non-EU migrant who is earning less than a set amount, said to be between £31,000 and £49,000, restricted from staying in the country.

"One cannot identify the next generation of entrepreneurs or Nobel laureates only a few years into their careers, and certainly not just by looking at how much they are paid," the letter states.

The committee calculated that setting the salary benchmark at £35,000 would reduce the number of non-EU migrants by two-thirds, but cut UK domestic product by 0.29% within five years.